Huang Haishen, Ai Liqiang, Chen Min, Lü Yongjun
School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China.
Department of Engineering Mechanics, Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, P. R. China.
Phys Chem Chem Phys. 2021 Feb 19;23(6):3942-3948. doi: 10.1039/d0cp05828a.
We investigate the melting process of polycrystalline copper doped with hydrogen atoms by using the newly developed Cu/H ReaxFF force field. Hydrogen atoms are found to effectively promote the melting of copper, and even make it happen at temperatures below the equilibrium melting temperature of copper during rapid heating. The enhanced melting is closely relevant to the interaction of hydrogen atoms with the grain boundary. We find that host Cu atoms perform cooperative vibration around the grain boundaries as the precursor of premelting. The doping of hydrogen atoms is shown to drive the vibration more violent so that the grain boundary becomes broader and the premelting is prematurely triggered. Meanwhile, hydrogen atoms segregated in grain boundaries massively diffuse into the bulk region with increasing temperature, resulting in intensification of lattice distortion of the bulk phase. This facilitates the rapid advancement of the liquid-solid interface during melting in contrast to the slow and discontinuous interface advancement in hydrogen-free polycrystalline copper. Our results suggest that even a small amount of hydrogen atoms is expected to significantly affect the thermodynamic properties of metals with the existence of structural defects.
我们使用新开发的Cu/H ReaxFF力场研究了掺杂氢原子的多晶铜的熔化过程。发现氢原子能够有效地促进铜的熔化，甚至在快速加热过程中使其在低于铜的平衡熔化温度的温度下发生熔化。增强的熔化与氢原子与晶界的相互作用密切相关。我们发现主体铜原子在晶界周围进行协同振动，作为预熔化的前兆。氢原子的掺杂使振动更加剧烈，从而使晶界变宽并过早触发预熔化。同时，随着温度升高，在晶界偏析的氢原子大量扩散到体相区域，导致体相晶格畸变加剧。与无氢多晶铜中缓慢且不连续的液 - 固界面推进相比，这有利于熔化过程中液 - 固界面的快速推进。我们的结果表明，即使存在少量氢原子，在存在结构缺陷的情况下也有望显著影响金属的热力学性质。
